Fatty acids bearing chemical modifications in addition to the common double bonds are found in the storage lipids of many oilseeds (Harwood, J. L. (1980) In The Biochemistry of Plants, T. S. Moore Jr., ed. CRC Press, New York, pp 91–116). Some of these modifications functionalize the fatty acid to produce products that are useful in industrial applications; this is opposed to the more common usage of plant-derived lipids as foods. Examples are the use of the hydroxylated fatty acid ricinoleic acid in lubricants, and the short- or medium-carbon chain length fatty acids from palm oil in detergents. In some cases, fatty acid composition of the storage lipids of oilseeds produced in temperate climates can be modified by the addition of genes from exotic sources so that large amounts of unique fatty acids are produced (Ohlrogge, J. B. (1994) Plant Physiol. 104, 821–826).
Fatty acids containing conjugated double bonds are major components of the seed oil of a limited number of plant species. For example, α-parinaric acid (9-cis, 11-trans, 13-trans, 15-cis-octadecatetraenoic acid) and β-parinaric acid (9-trans, 11-trans, 13-trans, 15-cis-octadecatetraenoic acid) compose more than 25% of the total fatty acids of the seed oil of Impatiens species (Bagby, M. O., Smith, C. R. and Wolff, I. A. (1966) Lipids 1, 263–267). In addition, α-eleostearic acid (9-cis, 11-trans, 13-trans-octadecatrienoic acid) and β-eleostearic acid (9-trans, 11-trans, 13-trans-octadecatrienoic acid) compose >55% of the total fatty acids of the seed oil of Momordica charantia (Chisolm, M. J. and Hopkins, C. Y. (1964) Can. J. Biochem. 42, 560–564; Liu, L., Hammond, E. G. and Nikolau, B. J. (1997) Plant Physiol. 113, 1343–1349).
The presence of conjugated double bonds in fatty acids provides the functional basis for drying oils such as tung oil that are enriched in isomers of eleostearic acid. This is due largely to the fact that fatty acids with conjugated double bonds display high rates of oxidation, particularly when compared to polyunsaturated fatty acids with methylene interrupted double bonds. Drying oils, such as tung oil, are used as components of paints, varnishes, and inks.
Conjugated fatty acids can also be used as an animal feed additive. Conjugated linoleic acids (CLAs, 18:2) have been used to improve fat composition in feed animals.
U.S. Pat. No. 5,581,572, issued to Cook et al. on Dec. 22, 1998, describes a method of increasing fat firmness and improving meat quality in animals using conjugated linoleic acds.
U.S. Pat. No. 5,554,646, issued to Cook et al. on Sep. 10, 1996, describes a method of reducing body fat in animals using conjugated linoleic acids.
U.S. Pat. No. 5,519,451, issued to Cook et al. on Jul. 6, 1999, describes a method of improving the growth or the efficiency of feed conversion of an animal which involves animal feed particles having an inner core of nutrients and an outer layer containing a conjugated fatty acid or an antibody that can protect the animal from contacting diseases that can adversely affect the animal's ability to grow or efficiently convert its feed into body tissue.
U.S. Pat. No. 5,428,072, issued to Cook et al. on Jun. 27, 1995, describes a method of enhancing weight gain and feed efficienty in animal which involves the use of conjugated linoleic acid.
The mechanism by which these effects are realized is not known. It is believed that no one heretofore has discussed the use of conjugated 18:3 fatty acids (conjugated linolenic acids or ClnAs), for improving animal carcass characteristics.
The biosynthesis of fatty acids with conjugated double bonds is not well understood. Several reports have indicated that conjugated double bonds are formed by modification of an existing double bond (Crombie, L. and Holloway, S. J. (1985) J. Chem. Soc. Perkins Trans. I 1985, 2425–2434; Liu, L., Hammond, E. G. and Nikolau, B. J. (1997) Plant Physiol. 113, 1343–1349). For example, the double bonds at the 11 and 13 carbon atoms in eleostearic acid have been shown to arise from the modification of the Δ12 double bond of linoleic acid (18:2Δ9,12) (Liu, L., Hammond, E. G. and Nikolau, B. J. (1997) Plant Physiol. 113, 1343–1349). The exact mechanism involved in conjugated double formation in fatty acids, however, has not yet been determined. Thus, while candidate enzyme classes have been suggested, no gene sequences have been isolated from those candidate classes and from tissues that are known to produce fatty acids with conjugated double bonds.